UFH - heat all zones or only those used

[richie9648]

This might sound like a daft question so please bear with me !!!

 

I had my UFH commissioned a few months and so far loving it. I’ve been trying to understand gas usage and how that differs if different zones are on? Currently we have 4 zones but given we are usually in just one zone most of the day, that one is on most of the time. 
 

the problem comes when child no1 wants to go and play in another room - it’s cold and takes a while to heat up. 
 

So my question is - if I just whack all zones on all at the same time, does that use more gas or does it just use the same amount of gas and flow is restricted as it’s going to more places so takes longer to heat. 
 

i an not technical and prob a daft question so just wanted to know!!

 

thanks 

[JohnMo]

Last year I had lots of zone on at differing times, this year I have all zones on if any zone is on and I am using 25% less mostly, in some months 40% less gas.

 

The issue with just one zone on is the boiler cannot get rid of the heat quickly enough, so stop starts runs for a very short period and does this quite a lot.  So efficiency drops of a cliff.

 

I tried lots of things a monitored gas consumption and the weather to build a trend so I could understand what worked best.

Edited January 22, 2023 by JohnMo
Miss the word gas

[Kelvin]

I did lots of tests of this in the previous house and came to the conclusion that heating up the whole floor with the occasional rooms setback a bit seemed to be the most efficient option. I did a spreadsheet tracking it that covered two years but can’t find it! 

[richie9648]

Interesting !! Thanks for the feedback - looks as if there’s some science to it !! 

[V1ks]

I have a system boiler with 4 port manifold and I have two zones, kitchen is Tiles and living room is LVT and i find that when the UFH is On in the kitchen the boiler cant get rid off the heat quickly and would go into the anticycle mode often, so it would reach the target temp of 60c and then id get the egg timer while the pump is running. However i noticed that when both zones are on the boiler is happy to be at around 60c constant while the UFH is on and return temp at about 54c (i believe the  ideal condensing temp).  Also if one zone + Some rads are running the boiler doesn't go into anticycle mode. 

 

 

 

[jayc89]

If you have a buffer tank, this should take care of the efficiency concerns, so only heat the rooms as you need to. If you don't, like me, I've also found it cheaper to heat the slab as a single zone. 

[JohnMo]

Dump the zones go single zone, balance the flow rates to equalise the heat dumped in to room. Gas boilers are usually way to big and struggle on low heat demands.